Four-component varifocal attachment with movable negative lens members



Aug. 23, 1966 MAHER ETAL FOUR-COMPONENT VAHIFOCAL ATTACHMENT WITH MOVABLE NEGATIVE LENS MEMBERS Flled Jan 21 1965 d v z arl djd5d6 d7 Karl Macher GUnfer Klemf INVENTOR.

AGENT United States Patent 3,267 803 FOUR-COMPONENT VARIFOCAL ATTACHMENT WITH MOVABLE NEGATIVE LENS MEMBERS Karl Macher and Giinter Klemt, Bad 'Kreuznach, Ger- 3,267,803 Patented August 23, 1966 "ice the radius of its front surface be at least equal to the absolute value of the radius of its rear surface.

The invention will be described in greater detail with reference to the sole figure of the accompanying drawing many, assignors to I05. Schneider & Co., Bad Kreuzwhich shows a varifocal front attachment embodying the nach, Germany, a corporation of Germany i i 1! 1965, 1 196 The system shown in the drawing is a four-component Claims prlonty, applicaltliogs gg h or attachment consisting of a fixed front component I of positive refractivity, a first movable intermediate compo- 2Cla1ms. (Cl.8857) nent II of negative refractivlty, a second movable inter- This application -is a .continuation-in-part of our comediate component III also of negative refractivity, and Pending application filed y 1961, a fixed, positively refracting rear component IV. Comand now abandoned. ponent I consists of a biconvex singlet L1 (radii r1, r2 In 0 1' US. Patent issued 1962, and thickness d1) and, separated from it by a small air and also in our aforementioned application Ser. No. 126,- space d2, of a doublet composed of a positive lens L2 307, there have been disclosed varifocal attachments for (radii r3, r4 and thickness d3) and a negative lens L3 camera objectives designed to reduce the aberrations nor- (radii r4, r5 and thickness d4). A variable air space d5 mally encountered in such systems; they include a fixed separates this doublet from component II which consists positively refractive front component on the object side of a positive lens L4 (radii r6, r7 and thickness d6) ccof the system, a fixed positively refractive rear compomented onto a negative lens L5 (radii r7, r8 and thickness nent on the image side, or side of the shorter light rays, d7). Another variable air space d8 exists between lens and two movable intermediate components of negative re- L5 and component III which consists of a negative lens L6 fractivity and of relatively small dimensions. Whereas (radii r9, r10 and thickness d9) cemented onto a positive the attachment disclosed in US. Patent No. 3,057,257 lens L7 (radii r10, r11, thickness d10). The latter lens has a varifocal ratio of about 1:4 realizable with an aperis separated by a variable air space dll from component ture ratio of 1:2.8, it is the object of the present inven- IV which consists of a positive lens L8 (radii r12, r13 tion to improve both these ratios while maintaining the and thickness d12) cemented onto a negative lens L9 residual aberrations of the system small and substantially (radii r13, r14 and thickness r113). constant throughout the range of adjustment. Representative values for the radii r1 to r14 and the The foregoing object is realized, in accordance with a thicknesses and separations d1 to d13 of lenses L1 to L9, feature of this invention, by the provision of an essentially based upon a reference parameter of numerical value 100 afocal attachment of the type described above wherein, which may be the median focal length of an objective preferably, each of the components has at least one cesystem including the illustrated attachment, along with mented surface and wherein the focal lengths of the two their refractive indices n and the Abb numbers 2, are movable negative components difier by not more than given in the following Table I for a system which retains 125%; advantageously, as in the systems disclosed in the its afocal character in all positions of adjustment and patent and the application referred to, the focal length whose linear magnification ratio varies from 0.56 to 2.6, of the fixed rear component is equal to or less than 75% this corresponding to a varifocal ratio of about 1:5; the of that of the fixed front component. It has further been system is particularly adapted for use with objectives for found that, for minimizing spherical aberrations, the rear 8-mm. film cameras having a focal length of 13 mm. and component should be biconvex and so proportioned that an aperture ratio of 1:1.8.

TABLE I Thlcknesses Component Lens Radii and 12. v

Separations n 55.92 L1 d1 8.00 1. 58913 01.2

r; =+as1.00 I a, 0.14 Air space fi=+65.25. {Ts 57.94

(is =10.10 1. 62041 00. 3 n =-139.00 til 2.00 1. 80518 25.5

d 1.22 Variable Air Space Y'd =+381.00 II 6 3.15 1.80518 25.5 f11=-'.27.16 r 83.90

d =19.25 Variable Air Space r, 20.95 111 do 1.00 1. 71300 53.9 flll='-25.49 r 21.45

d10= 1.80 1.80518 25.5 Tu=+ 88.56

dn =13.54 Variable Air Space m=+ 55.02 W dn= 2.30 1. 65830 51.3 frv=+35.29 T13= 10.48

totnl= 3 The air spaces d5, d8 and till may be varied concurrently in order to change the magnification ratio of the system within the aforestated limits in accordance with the following Table II:

TABLE II Variable Air Spaces Magnification Ratio From the foregoing Table I it will be noted that the focal length i of the rear component IV, having a magnitude of 35.29, is less than 75% of the focal length f; of the front component I, having a magnitude of 65.25; also the focal length i of component II, of magnitude 27.16, will be seen to exceed the focal length f of component HI, having a magnitude of 25.49, by less than 25%. The radius r12 of the front surface of the rear component IV is greater than the absolute value of the radius r14 of the corresponding rear surface to minimize spherical aberration. Such aberration is further suppressed by the fact that the cemented internal surface r13 of the biconvex doublet L8, L9, constituting component IV, is strongly curved toward the image side of the system and is collective in'character since the refractive index of lens L8 exceeds that of lens L9.

We claim:

1. A varifocal attachment for an optical objective, consisting of four components separated from one another by variable air spaces and together constituting an afocal system, said components including a fixed front component of positive refractively constituted by two air-spaced positive members of strong forward convexity of which the first one is a singlet and the second one is a doublet, a first movable intermediate component constituted by a doublet of negative refractivity, a second movable intermediate component constituted by a doublet of negative refractivity, and a fixed rear component of positive refractivity, said rear component having a focal length equal to at most 75 of the focal length of said front component, the focal length of said first intermediate component exceeding that of said second intermediate component in absolute value and differing from it by at most 25%, said rear component being a biconvex doublet having a front surface whose radius of curvature at least equals in absolute magnitude the radius of curvature of its rear surface, said biconvex doublet further having a collective internal surface strongly curved toward the im age side of the system.

2. An attachment according to claim 1 wherein the radii r1 to r14 and the thicknesses and separations d1 to d13 of the lensesLl to L9 forming part of said front component I, said first intermediate component II, said second intermediate component HI and said fourth intermediate component 1V, based upon a reference parameter of numerical value 100, the indices of refraction n of all of said lenses and their Abb numbers 1: have numerical values substantially as given in the following table:

TABLE I Thicknesses Component Lens Radii an m r Separations d1 0.14 Air ipace I r; 57.94

Ln is =10.10 1. 62041 60. 3

=-139.00 La dd 2.00 1.80518 25. 5

d 1.22 Variable Air Space n =+381.00 L4 do 3.15 1.80518 25.5 II 83.90

Ls d1 1.00 1. 58913 61. 2

d; =l9.25 Variable Air Space n 20.95 Lu do 1.00 1. 71300 53.9 III rw=+ 21.45

du=13.54 Variable Air Space T11=+ 55.92 L; d 2.80 1. 65830 57. 3 IV T13=-- 10.48

Lo du= 1.00 1. 62588 35.6

References Cited by the Examiner UNITED STATES PATENTS 2,746,350 5/1956 Hopkins 88-57 3,027,805 4/1962 Yamap 88-57 JEWELL H. PEDERSEN, Primary Examiner.

I. K. CORBIN, Assistant Examiner. 

1. A VARIFOCAL ATTACHMENT FOR AN OPTICAL OBJECTIVE, CONSISTING OF FOUR COMPONENTS SEPARATED FROM ONE ANOTHER BY VARIABLE AIR SPACES AND TOGETHER CONSISTING AN AFOCAL SYSTEM, SAID COMPONENTS INCLUDING A FIXED FRONT COMPONENT OF POSITIVE REFRCATIVELY CONSTITUTED BY TWO AIR-SPACED POSITIVE MEMBERS OF STRONG FORWARD CONVEXITY OF WHICH THE FIRST ONE IS A SINGLET AND THE SECOND ONE IS A DOUBLET, A FIRST MOVABLE INTERMEDIATE COMPONENT CONSTITUTED BY A DOUBLET OF NEGATIVE REFRACTIVITY, A SECOND MOVABLE INTERMEDIATE COMPONENT CONSTITUTED BY A DOBULET OF NEGATIVE REFRACTIVITY, AND A FIXED REAR COMPONENT OF POSITIVE REFRACTIVITY, SAID REAR COMPONENT HAVING A FOCAL LENGTH EQUAL TO AT MOST 75% OF THE FOCAL LENGTH OF SAID FRONT COMPONENT, THE FOCAL LENGTH OF SAID FIRST INERMEDIATE COMPONENT EXCEEDING THAT OF SAID SECOND INTERMEDITE COMPONENT IN ABSOLUTE VALUE AND DIFFEREING FROM IT BY AT MOST 25%, SAID REAR COMPONENT BEING A BICONVEX DOUBLET HAVING A FRONT SURFACE WHOSE RADIUS OF CURVATURE AT LEAST EQUALS IN ABSOLUTE MAGNITUDE THE RADIUS OF CURVATURE OF ITS REAR SURFACE, SAID BICONVEX DOUBLET FURTHER HAVING A COLLECTIVE INTERNAL SURFACE STRONGLY CURVED TOWARD THE IMAGE SIDE OF THE SYSTEM 